CHAP. XXII.] MOLLUSCA. 507 



Class.— GASTEKOPODA. 



Order I.—PROSOBBANCHIATA. 



Family 1.— STEOMBID^. (4 Genera, 86 Species.) 



DiSTKiBUTiON. — The Strombidse, or Wing-shells, inhabit tropi- 

 cal and warm seas from the Mediterranean to New Zealand ; most 

 abundant in the Indian and Pacific Oceans. There are nearly 

 200 fossil species, from the Lias to Miocene and recent deposits. 



Family 2.— MUEICID^. (12 Genera, 1000 Species.) 



Distribution. — All seas, most abundant in the Tropics. 

 TricJiotropis is confined to Northern seas ; Murex and Fusus are 

 cosmopolitan. There are about 700 fossil species, ranging from 

 the Oolite to the Miocene and recent formations. 



Family 3.— BUCCINID^. (24 Genera, 1100 Species.) 



DiSTKiBUTiON. — The Buccinidse, or " Whelks," range over the 

 whole world, but some of the genera are restricted. Buccinum 

 inhabits the north and south temperate seas; Monoceros the 

 West Coast of America ; Cassidaria the Mediterranean ; Phos, 

 Harpa, Eburna, and Ricimda, are confined to the Pacific ; Dol- 

 ium inhabits the Mediterranean as well as the Pacific. There 

 are about 350 fossil species, mostly from the Eocene and Miocene 

 beds. 



